feat: V1 prototype — Vite/React/TS tileset generator

- Scaffold: package.json, tsconfig.json, vite.config.ts, index.html
- src/lib/imageProcessor.ts: full pipeline (normalize, offset, seam repair, export, validation)
- src/components/UploadPanel.tsx: drag-and-drop, file picker, clipboard paste
- src/components/SettingsPanel.tsx: all controls per spec
- src/components/PreviewPanel.tsx: Original / Tileable / Repeated tabs
- src/components/ErrorBanner.tsx: dismissible error/warning banners
- src/App.tsx: root component wiring everything together
- src/index.css: dark premium glassmorphism theme w/ Inter font

node_modules/postcss/lib/postcss.d.mts

@@ -0,0 +1,66 @@
+export {
+  // Type-only exports
+  AcceptedPlugin,
+  AnyNode,
+  atRule,
+  AtRule,
+  AtRuleProps,
+  Builder,
+  ChildNode,
+  ChildProps,
+  comment,
+  Comment,
+  CommentProps,
+  Container,
+  ContainerProps,
+  CssSyntaxError,
+  decl,
+  Declaration,
+  DeclarationProps,
+  // postcss function / namespace
+  default,
+  document,
+  Document,
+  DocumentProps,
+  FilePosition,
+  fromJSON,
+  Helpers,
+  Input,
+  JSONHydrator,
+  // This is a class, but it’s not re-exported. That’s why it’s exported as type-only here.
+  type LazyResult,
+  list,
+  Message,
+  Node,
+  NodeErrorOptions,
+  NodeProps,
+  OldPlugin,
+  parse,
+  Parser,
+  // @ts-expect-error This value exists, but it’s untyped.
+  plugin,
+  Plugin,
+  PluginCreator,
+  Position,
+  Postcss,
+  ProcessOptions,
+  Processor,
+  Result,
+  root,
+  Root,
+  RootProps,
+  rule,
+  Rule,
+  RuleProps,
+  Source,
+  SourceMap,
+  SourceMapOptions,
+  Stringifier,
+  // Value exports from postcss.mjs
+  stringify,
+  Syntax,
+  TransformCallback,
+  Transformer,
+  Warning,
+  WarningOptions
+} from './postcss.js'